Pump unit and working vehicle

ABSTRACT

A pump unit for supply and discharge of hydraulic fluid into and from an actuator upon receiving driving power from a driving source is provided, in which said actuator is fluidly connected to said pump unit via a hydraulic circuit. The pump unit includes an input member operatively connected to the driving source, a first hydraulic pump body operatively connected to the input member, a pump case for accommodating the first hydraulic pump body and forming a hydraulic fluid sump, and a PTO unit accommodated within the pump case. The PTO unit includes a PTO shaft supported by the pump case so as to have an end extending outward from the pump case, and a clutch mechanism for selectively enabling and disabling transmission of driving power from the input member to the PTO shaft.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priorities from Japanese Patent Application Nos.2002-101100 and 2002-112128, which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump unit that is operativelyconnected to a driving source and fluidly connected to an actuator via ahydraulic circuit so as to be capable of outputting driving power withvariable speed through the actuator.

2. Related Art

The hydraulic pump unit is used in various fields of applications, oneof which is directed to a cooperative operation with the actuator whichis arranged away from the hydraulic pump unit. In this application, thehydraulic pump unit and the actuator are connected to each other via ahydraulic circuit so as to together constitute a main transmission pathfor receiving driving power from a driving source and outputting thesame with variable speed.

In some applications, a power transmission structure equipped with thehydraulic pump unit requires a sub transmission path in addition to themain transmission path. Such a requirement exists, for example, in alawn mower, in which power from a common driving source is divided andoutput into a running-power transmission path and a PTO powertransmission path.

Now, the description will be made for the arrangement where a hydraulicmotor unit is used as the actuator.

U.S. Pat No. 4,395,865 (hereinafter referred to '865 patent), U.S. Pat.No. 5,809,756 (hereinafter referred to '756 patent) and other prior artreferences disclose a lawn mower that includes a PTO power transmissionpath for receiving power from an engine and outputting the same to amower as well as a running power transmission path that is made up of ahydraulic pump unit operatively connected to the engine and a hydraulicmotor unit located away from the hydraulic pump unit so as to drivedriving wheels.

Specifically, the lawn mower in the '865 patent provides the engine as acommon driving source with first and second output shafts, which arerespectively and operatively connected to the hydraulic pump unit and amower unit. That is, in the lawn mower of the '865 patent, the runningpower transmission path is entirely separated from the PTO powertransmission path. However, this entire separation of the running powertransmission path and the PTO power transmission path necessitates alarge number of parts for separately forming these transmission pathsand a large space for accommodating these separate transmission paths.Also, the power transmission structure with two separate powertransmission paths requires independent control for enabling anddisabling the transmission of power in each transmission path. In orderto achieve this control, in the lawn mower of the '865 patent, anelectromagnetic clutch for enabling and disabling the transmission ofpower is placed in each transmission path. This electromagnetic clutchhas however poor durability, and therefore may result in loss inreliability to each transmission path.

On the other hand, the lawn mower of the '756 patent provides the enginewith a common output shaft, on which a driving pulley and a mower pulleyare supported, so that power can be divided into the running powertransmission path and the PTO power transmission shaft through thiscommon output shaft. In order to achieve this arrangement, the commonoutput shaft must be lengthened, which results in a larger load appliedthereon. The '756 patent is also silent as to how to enable and disablethe transmission of power in each transmission path.

The present invention has been conceived in consideration of the aboveprior arts. Accordingly, it is an object of the present invention toprovide a pump unit that is operatively connected to a driving sourceand fluidly connected to an actuator via a hydraulic circuit so as tooutput driving power with variable speed through the actuator, and has asimplified structure enabling dividing driving power from the drivingsource into a sub transmission path as well as into a main transmissionpath, which the pump unit constitutes in cooperation with the actuator.

It is another object of the present invention to provide a workingvehicle having a simplified structure, which includes a PTO powertransmission path extending from a drive source to a working unit forland treatment such as a mower unit (hereinafter simply referred to as“working unit”), as well as a running power transmission path that ismade up of a hydraulic pump unit for receiving driving power from adriving source, and a hydraulic motor unit located away from thehydraulic pump unit and fluidly connected thereto.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided apump unit for supply and discharge of hydraulic fluid into and from anactuator upon receiving driving power from a driving source, in whichthe actuator is fluidly connected to the pump unit via a hydrauliccircuit. The pump unit includes an input member operatively connected tothe driving source, a first hydraulic pump body operatively connected tothe input member, a pump case for accommodating the first hydraulic pumpbody and forming a hydraulic fluid sump, and a PTO unit accommodatedwithin the pump case. The PTO unit includes a PTO shaft supported by thepump case so as to have an end extending outward from the pump case, anda clutch mechanism for selectively enabling and disabling transmissionof driving power from the input member to the PTO shaft.

With the thus arranged pump unit, it is possible to easily make up areduced-size sub transmission path that can be controlled independentlyof the main transmission path, while making up the main transmissionpath in cooperation with the actuator fluidly connected to the pumpunit. Also, since the operation to enable and disable the powertransmission is performed by the clutch mechanism, the sub transmissionpath can have an improved durability.

Preferably, the pump case has an opening, and the pump unit furtherincludes a center section connected to the pump case so as to close theopening, while supporting the first hydraulic pump body on one ofopposite sides thereof, in which the hydraulic circuit is disposed inthe center section.

The pump unit may further include a charge pump unit for suckinghydraulic fluid from the hydraulic fluid sump and discharging the sameto the hydraulic circuit, in which the charge pump unit is operativelyconnected to the input member and supported on the opposite side of thecenter section.

With the thus arranged pump unit, the charge pump unit can be used as afluid supply source for supplying pressurized hydraulic fluid to thehydraulic circuit, thereby achieving easy supply of pressurizedhydraulic fluid to the hydraulic circuit.

The pump unit may further include a second hydraulic pump bodyoperatively connected to the input member, in which the opening of thepump case is adapted to enable the first and second hydraulic pumpbodies to pass therethrough, and the center section is connected to thepump case so as to close the opening, while supporting the first andsecond hydraulic pump bodies.

The PTO unit may further include a brake mechanism for releasing andapplying braking force away from and to the PTO shaft in associationwith the operation of the clutch mechanism to enable and disable thetransmission of driving power from the input member to the PTO shaft.With this arrangement, it is possible to effectively prevent the PTOshaft from continuing to rotate by inertia when the power transmissionto the PTO shaft has been disabled.

The PTO unit may further include a brake mechanism for releasing andapplying braking force away from and to the PTO shaft in associationwith the operation of the clutch mechanism to enable and disable thetransmission of driving power from the input member to the PTO shaft, inwhich the brake mechanism and the clutch mechanism are of hydraulic typethat is operated by hydraulic fluid discharged by the charge pump unit.With this arrangement, the charge pump unit can be used as a fluidsupply source for supplying pressurized hydraulic fluid to the hydraulicclutch mechanism and the hydraulic brake mechanism, thereby achieving asimplified structure of a hydraulic circuit of each of the hydraulicclutch mechanism and the hydraulic brake mechanism.

The pump unit may further include an input shaft acting as the inputmember, and a first pump shaft for driving the first hydraulic pumpbody.

In the above pump unit, the PTO shaft may be arranged coaxially with theinput shaft.

With the thus arranged pump unit, the sub transmission path from thedriving source to the working unit can be formed substantially in alinear fashion, thereby achieving a simplified structure of the subtransmission path and occupation of less space by the pump unit.

According to another aspect of the present invention, there is provideda working vehicle that includes a vehicle frame, a first pair oflaterally disposed wheels supported by the vehicle frame, a second pairof laterally disposed wheels supported by the vehicle frame so as to belocated away from the first pair of laterally disposed wheels in a foreand aft direction of the working vehicle, a working unit supported bythe vehicle frame, a driving source supported by the vehicle frame,first and second motor units respectively and operatively connected tothe first pair of laterally disposed wheels, and a pump unit supportedby the vehicle frame so as to be operatively connected to the drivingsource. The pump unit is arranged to supply and discharge hydraulicfluid into and from each of the first and second motor units, and takeout driving power of the driving source and output the same as drivingpower for the working unit. The pump unit includes an input memberoperatively connected to the driving source, a first hydraulic pump bodyoperatively connected to the input member, a pump case for accommodatingthe first hydraulic pump body, and a PTO unit accommodated within thepump case. The PTO unit includes a PTO shaft supported by the pump caseso as to have an end extending outward from the pump case, and a clutchmechanism for selectively enabling and disabling transmission of drivingpower from the input member to the PTO shaft.

With the thus arranged working vehicle, it is possible to easily make upa reduced-size sub transmission path that can be controlledindependently of the main transmission path, while making up the maintransmission path in cooperation with the actuator fluidly connected tothe pump unit. Also, since the operation to enable and disable the powertransmission is performed by the clutch mechanism, the sub transmissionpath can have an improved durability.

The working vehicle may further include a charge pump unit that isoperatively connected to the input member. With the thus arrangedworking vehicle, the charge pump unit can be used as a fluid supplysource for supplying pressurized hydraulic fluid to the hydrauliccircuit, thereby achieving easy supply of pressurized hydraulic fluid tothe hydraulic circuit.

The pump unit may further include a second hydraulic pump bodyoperatively connected to the input member.

The PTO unit may further include a brake mechanism for releasing andapplying braking force away from and to the PTO shaft in associationwith the operation of the clutch mechanism to enable and disable thetransmission of driving power from the input member to the PTO shaft.

With the thus arranged working vehicle, it is possible to effectivelyprevent the PTO shaft from continuing to rotate by inertia when thepower transmission to the PTO shaft has been disabled.

The driving source may be supported on the vehicle frame in vibrationfree manner, while the pump unit is fixedly supported on the vehicleframe, and the driving source is operatively connected to the inputmember via vibration-absorbing transmission means.

The driving source may be supported on the vehicle frame in vibrationfree manner, while the pump unit is integrally connected to the drivingsource.

The pump unit may further include an input shaft acting as the inputmember, and a first pump shaft operatively connected to the input shaftand arranged to drive the first hydraulic pump body.

The PTO shaft may be arranged coaxially with the input shaft. With thisarrangement, the sub transmission path from the driving source to theworking unit can be formed substantially in a linear fashion, therebyachieving a simplified structure of the sub transmission path andoccupation of less space by the pump unit.

In the thus arranged working vehicle, the PTO shaft may have an axis,which is located at the same position as an axis of the input shaft in avehicle width direction, and is arranged substantially orthogonal to theaxis of the input shaft.

The pump unit may further include a first pump shaft that acts as theinput member and is arranged to drive the first hydraulic pump body. Thefirst pump shaft may be arranged substantially parallel to the PTOshaft. As an alternative thereto, the first pump shaft may be arrangedsubstantially orthogonal to the PTO shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, and other objects, features and advantages of the presentinvention will become apparent from the detailed description thereof inconjunction with the accompanying drawings wherein.

FIGS. 1A and 1B are respectively a side view and a plan view of a lawnmower, to which a pump unit of a first embodiment of the presentinvention has been applied.

FIG. 2 is a hydraulic circuit diagram of the pump unit according to thefirst embodiment.

FIG. 3 is a plan view in horizontal cross section of the pump unitaccording to the first embodiment.

FIG. 4 is a side view in vertical cross section of the pump unit of FIG.3.

FIG. 5 is a plan view of the pump unit having a hydraulic brakemechanism of another embodiment with a part in horizontal cross section.

FIG. 6 is a plan view of the lawn mower, to which the pump unit of asecond embodiment has been applied.

FIG. 7 is a plan view in horizontal cross section of the pump unitaccording to the second embodiment.

FIGS. 8A and 8B are a side view and a plan view of the lawn mower, towhich the pump unit of a third embodiment has been applied.

FIG. 9 is a plan view in horizontal cross section of the pump unitaccording to the third embodiment.

FIG. 10 is a side view in vertical cross section of the pump unitaccording to the third embodiment.

FIG. 11 is a cross section taken along the line XI—XI in FIG. 9.

FIG. 12 is a plan view of the lawn mower, to which the pump unitaccording to a modified example of the third embodiment has beenapplied.

FIG. 13 is a plan view in horizontal cross section of the pump unitaccording to the modified example of the third embodiment.

FIGS. 14A and 14B are a side view and a plan view of the lawn mower, towhich the pump unit of a fourth embodiment of the present invention hasbeen applied.

FIG. 14C is a plan view of the lawn mower, to which the pump unitaccording to a modified example of the fourth embodiment has beenapplied.

FIG. 15 is a hydraulic circuit diagram of the pump unit of the fourthembodiment.

FIG. 16 is a plan view in horizontal cross section of the pump unitaccording to the fourth embodiment.

FIG. 17 is a side view in vertical cross section of the pump unit ofFIG. 16.

FIG. 18 is a cross section taken along the line XVIII—XVIII in FIG. 16.

FIG. 19 is a cross section taken along the line XIX—XIX in FIG. 16.

FIG. 20 is a plan view of the pump unit equipped with a hydraulic brakemechanism according to another embodiment with a part in horizontalcross section.

FIGS. 21A and 21B are a side view and a plan view of the lawn mower, towhich the pump unit of a fifth embodiment of the present invention hasbeen applied.

FIG. 21C is a plan view of the lawn mower, to which the pump unitaccording to a modified example of the fifth embodiment has beenapplied.

FIG. 22 is a plan view in horizontal cross section of the pump unitaccording to the fifth embodiment.

FIG. 23 is a cross section taken along the line XXIII—XXIII in FIG. 22.

FIG. 24 is a cross section taken along the line XIV—XIV in FIG. 22.

FIGS. 25A and 25B are a side view and a plan view of the lawn mower, towhich the pump unit of a sixth embodiment of the present invention hasbeen applied.

FIG. 26 is a side view in vertical cross section of the pump unitaccording to the sixth embodiment.

FIG. 27 is a plan view of the lawn mower, to which the pump unit of aseventh embodiment of the present invention has been applied.

FIG. 28 is a plan view in horizontal cross section of the pump unitaccording to the seventh embodiment of the present invention.

FIG. 29 is a plan view of the lawn mower, to which the pump unit of amodified example of the seventh embodiment has been applied.

FIG. 30 is a plan view in horizontal cross section of the pump unitaccording to the seventh embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

First Embodiment

The description will be made for the first embodiment of the presentinvention with reference to the accompanied drawings.

The pump unit according to the present invention is fluidly connected toan actuator via a hydraulic circuit for a cooperative operation, inwhich the actuator is driven by the effect of pressurized hydraulicfluid in the hydraulic circuit. This embodiment will be hereinafterdescribed by taking for example the case where a hydraulic motor unit isused as the actuator.

FIGS. 1A and 1B are respectively a side view and a plan view of a lawnmower 100A, to which a pump unit 1 of this embodiment has been applied.FIG. 2 is a hydraulic circuit diagram of the pump unit 1. FIGS. 3 and 4are respectively a plan view in horizontal cross section and a side viewin vertical cross section of the pump unit according to this embodiment.

Now, the description will be made for the lawn mower 100A.

As illustrated in FIGS. 1A and 1B, the lawn mower 100A includes avehicle frame 110, a pair of laterally disposed driving wheels (rearwheels in this embodiment) 120 supported by the vehicle frame 110 so asto be located closer to a first side of the lawn mower (a rear side inthis embodiment), a pair of laterally disposed casters 130 supported bythe vehicle frame 110 so as to be located closer to a second side of thelawn mower (a front side in this embodiment), a working unit (mower unitin this embodiment) 140 supported by the vehicle frame 110 so as to belocated between the pair of laterally disposed driving wheels 120 andthe pair of laterally disposed casters 130, a driving source 150supported by the vehicle frame 110 so as to be located opposite to theworking unit 140 with the driving wheels 120 therebetween relative to afore and aft direction of the vehicle (that is, located closer to therear side in this embodiment), and first and second hydraulic motorunits 160 a, 160 b having motor shafts respectively and operativelyconnected to the pair of laterally disposed driving wheels 120, as wellas the pump unit 1 of this embodiment.

As illustrated in FIGS. 1 and 2, the pump unit of this embodiment isfluidly connected via a hydraulic circuit to the hydraulic motor units160 a, 160 b, which are located away from the pump unit 1, and isdesigned to receive driving power from the driving source 150 and letthe working units 160 a, 160 b drive the driving wheels 120 by utilizingthe hydraulic effect of the hydraulic circuit. That is, the pump unit 1constitutes the running power transmission path as a main transmissionpath in cooperation with the hydraulic motor units 160 a, 160 b.

The pump unit 1 is also designed to be capable of taking off power fromthe main transmission path and outputting the same as driving power forthe working unit 140. That is, the pump unit also constitutes a part ofthe PTO power transmission path.

More specifically, as illustrated in FIGS. 3 and 4, the pump unit 1includes an input shaft 80 operatively connected to the driving source150, a first pump shaft 10 a operatively connected to the input shaft80, a first hydraulic pump body 20 a to be driven by the first pumpshaft 10 a, a second pump shaft 10 b operatively connected to the inputshaft 80 or the first pump shaft 10 a, a second hydraulic pump body 20 bto be driven by the second pump shaft 10 b, a pump case 30 foraccommodating the first hydraulic pump body 20 a and the secondhydraulic pump body 20 b and having a first opening 30 a through whichthe first and second hydraulic pump bodies 20 a, 20 b pass into and outof the pump case 30, a center section 40 connected to the pump case 30so as to close the first opening 30 a while supporting the first andsecond hydraulic pump bodies 20 a, 20 b, and a PTO unit 50 accommodatedwithin the pump case 30. The pump case 30 forms a hydraulic fluid sump.

As illustrated in FIG. 2, the first hydraulic pump body 20 a and thesecond hydraulic pump body 20 b are respectively and fluidly connectedto the first hydraulic motor unit 160 a and the second hydraulic motorunit 160 b via the hydraulic circuit (a pair of hydraulic lines 200 aand a pair of hydraulic lines 200 b in this embodiment).

The pump unit 1 of this embodiment is designed to have the pair ofhydraulic pump bodies 20 a, 20 b which respectively correspond to thepair of laterally disposed hydraulic motor units 160 a, 160 b so thatthe pair of driving wheels 120 can be driven at rotational speedsindependently of each other. That is, the pump unit 1 of this embodimentis designed so as to have the first hydraulic pump body 20 a and thesecond hydraulic pump body 20 b arranged respectively corresponding tothe first hydraulic motor unit 160 a and the second hydraulic motor unit160 b. However, the present invention is not necessarily limited to thisarrangement. The arrangement with only a single hydraulic pump body orwith three or more hydraulic pump bodies accommodated within the pumpcase 30 also falls within the scope of the present invention. Forexample, where the pump unit 1 is provided with only a single hydraulicpump body, the single hydraulic pump body is fluidly connected to thepair of laterally disposed hydraulic motor units 160 a, 160 b via ahydraulic circuit having a fluid dividing means such as a flow dividingvalve.

At least one of the hydraulic pump bodies 20 a, 20 b and the hydraulicmotor units 160 a, 160 b, which are respectively fluidly connected toeach other, is of a variable displacement type that varies thesuction/discharge rates by the operation of an output adjustment member.Accordingly, output with variable speed can be produced through motorshafts of the hydraulic motor units by controlling the slanting angle ofthe output adjustment member. In this embodiment, the hydraulic pumpbodies 20 a, 20 b are of the variable displacement type, while thehydraulic motor units 160 a, 160 b are of a fixed displacement type.

As best illustrated in FIG. 3, the input shaft 80 has an upstream endwith respect to the power transmission direction (a rear end in thisembodiment) supported by the pump case 30 so as to extend outwardsthrough the pump case 30 and operatively connected to the driving source150 via a flywheel 155. The flywheel 155 may be provided with a damper156 (see FIG. 1), thereby enabling power to be transmitted from thedriving source 150 to the input shaft 80, while limiting variation inangular speed of the output shaft of the driving source 150. As aresult, durability of the hydraulic pump bodies 20 a, 20 b can beimproved, hence achieving improved durability of the hydraulic motorunits 160 a, 160 b thanks to limited pulsation of hydraulic fluiddischarged from the hydraulic pump bodies 20 a, 20 b.

In this embodiment, as illustrated in FIG. 1, the driving source 150 issupported on the vehicle frame 110 in vibration free manner, while thepump case 30 is fixedly supported on the vehicle frame 110. Thisarrangement causes difference in vibration between the driving source150 and the pump case 30. In order to absorb this vibration difference,in this embodiment, the driving source 150 is operatively connected tothe input shaft 80 by a vibration-absorbing transmission means. In thisembodiment, as illustrated in FIG. 1, transmission shaft 170 havinguniversal joints at the opposite ends is used as the vibration-absorbingtransmission means. Instead, a belt transmission mechanism may beemployed.

As illustrated in FIG. 3, the first pump shaft 10 a is supported on thepump case 30 so as to be arranged substantially parallel to the inputshaft 80, and operatively connected to the input shaft 80 via a powertransmission mechanism 90. In this embodiment, the power transmissionmechanism 90 includes a drive-side gear 91 disposed non-rotatablyrelative to the input shaft 80 and a driven-side gear 92 disposednon-rotatably relative to the first pump shaft 10 a so as to be inmeshed engagement with the drive-side gear 91.

The first hydraulic pump body 20 a includes a piston unit 21 a thatperforms a rotational movement around the axis of the first pump shaft10 a by the rotation of the first pump shaft 10 a and a reciprocalmovement in association with the rotational movement, a cylinder block22 a that supports the piston unit 312, allowing it to freelyreciprocate, and is rotatably and sidably supported on the centersection 40 so as to be in communication with the pair of hydraulic lines200 a, and an output adjusting member 23 a (a combination of a movableswash plate and an operational shaft in this embodiment), whichregulates the stroke length of the piston unit 21 a according to theslanting angle so as to vary the suction/discharge rates of the pistonunit 21 a. In this embodiment, although the hydraulic pump bodies 20 a,20 b are of an axial piston type, it is possible to be of a radialpiston type.

The second pump shaft 10 b is supported on the pump case 30 so as to bearranged substantially parallel to the first pump shaft 10 a. The secondpump shaft 10 b is operatively connected to the input shaft 80 or thefirst pump shaft 10 a via a transmission mechanism 60 accommodatedwithin the pump case 30 so as to be rotated in synchronization with thefirst pump shaft 10 a. In this embodiment, the transmission mechanism 60includes a first gear 61 supported relatively non-rotatably on the firstpump shaft 10 a, and a second gear 62 having the same pitch as the firstgear 61 and relatively non-rotatably supported on the second pump shaft10 b so as to be in meshed engagement with the first gear 61.

The second hydraulic pump body 20 b has substantially the same structureas that of the first hydraulic pump body 20 a except that the secondhydraulic pump body 20 b is driven by the second pump shaft 10 b.Accordingly, the detailed description of the second hydraulic pump body20 b will be omitted.

As best illustrated in FIG. 3, the PTO unit 50 includes a PTO shaft 51and a hydraulic clutch mechanism 55. In this embodiment, the PTO shaft51 is aligned coaxially with the input shaft 80 and supported on thepump case 30 so as to have an outer end. In this embodiment, the end ofthe PTO shaft 51 extends forwards in the fore and aft direction of thevehicle.

More specifically, the PTO shaft 51 is aligned coaxially with the inputshaft 80 in operative connection to the input shaft 80 via thedrive-side gear 91, the driven-side gear 92, the first pump shaft 10 a,the first gear 61 and the hydraulic clutch mechanism 55, so that drivingpower from the input shaft 80 is selectively input to the PTO shaft 51by the hydraulic clutch mechanism 55. The outer end of the PTO shaft 51is operatively connected to an input part of the working unit 140 via avibration-absorbing transmission means. In this embodiment, transmissionshaft 175 having universal joints at the opposite ends is used as thevibration-absorbing transmission means, as illustrated in FIG. 1.

The coaxial arrangement of the input shaft 80 and the PTO shaft 51 inthe pump unit 1 of this embodiment produces the following effects:

As illustrated in FIG. 1B, the coaxial arrangement of the input shaft 80and the PTO shaft 51 can achieve the sub transmission path extendingfrom the driving source 150 to the working unit 140 in a linear fashion,and hence occupation of less space.

Where the connections between the driving source 150 and the input shaft80 and between the PTO shaft 51 and the working unit 140 arerespectively made by the transmission shafts 170, 175, the coaxialarrangement of the input shaft 80 and the PTO shaft 51 can reduce theload applied to connection areas between these shafts, hence achievingimproved durability of the connection areas and prevention of noises andvibrations. Specifically, the output shaft of the driving source 150 andthe input part of the working unit 140 are preferably locatedsubstantially along the longitudinal center axis of the vehicle in termsof the weight balance (see FIG. 1B). In this preferable arrangement,when the input shaft 80 and the PTO shaft 51 are offset to eitherlateral side from the longitudinal center axis of the vehicle, thetransmission shaft 170 between the driving source 150 and the inputshaft 80, or the transmission shaft 175 between the PTO shaft 51 and theworking unit 140 must be tilted at an angle relative to the longitudinalcenter axis. In order to achieve this orientation of the transmissionshaft, the universal joints at the opposite ends thereof are required toforcibly change the rotational axis of driving power to be transmitted.This causes a large load on these universal joints.

On the contrary, in this embodiment, as described above, the input shaft80 is aligned coaxially with the PTO shaft 51. This arrangement allowsthe transmission shafts 170, 175 to be aligned parallel to thelongitudinal center axis of the vehicle. As a result, it is possible toreduce the load applied on the universal joints provided on thetransmission shafts 170, 175.

Further, the PTO shaft 51 is vertically offset from the input part ofthe working unit 140 in consideration of the lifting height of theworking unit 140. Specifically, when the working unit 140 is at anoperational position (a position in contact with a land), thetransmission shaft 175 is tilted forwardly downwardly (see FIG. 1A),while at an inoperative position (a withdrawal position), thetransmission shaft 175 is horizontally oriented or is tilted forwardlyupwardly (not shown).

The universal joints can permit variation of tilting angle of thetransmission shaft 175 to some extent. However, when the PTO shaft 51and the input part of the working unit 140 are offset from each other inthe lateral direction of the vehicle, lateral bending as well asvertical vending are caused in the universal joints. As a result,“three-dimensional bending” occurs in the universal joints. On thecontrary, as described above, the coaxial arrangement of the PTO shaft51 and the input shaft 80 can omit the possibility to cause lateralbending and hence achieve the reduction of the load applied on theuniversal joints.

The hydraulic clutch mechanism 55 is designed to selectively enable anddisable power transmission from the input shaft 80 to the PTO shaft 51by the hydraulic effect. In this embodiment, as best illustrated in FIG.3, the hydraulic clutch mechanism 55 includes a drive-side member 55 arelatively rotatably and axially non-slidably supported on the PTO shaft51, while being operatively connected to the input shaft 80, adrive-side friction plate 55 b relatively non-rotatably and axiallyslidably supported on the drive-side member 55 a, a driven-side member55 c relatively non-rotatably supported on the PTO shaft 51, adriven-side friction plate 55 d relatively non-ratably supported on thedriven-side member 55 c in such a manner as to be axially slidablewithin a certain area, a clutch pressing member 55 e for bringing thedriven-side friction plate 55 d into frictional engagement with thedrive-side friction plate 55 b upon receiving the hydraulic effect, anda clutch biasing member 55 f for biasing the clutch pressing member 55 ein a direction away from the drive-side friction plate 55 b and thedriven-side friction plate 55 d.

The thus arranged hydraulic clutch mechanism 55 transmits power from theinput shaft 80 to the PTO shaft 51 via the drive-side member 55 a andthe driven-side member 55 c when the clutch pressing member 55 e hasbrought both the friction plates 55 b, 55 d into frictional engagementwith each other by the hydraulic effect, and disables power transmissionfrom the input shaft 80 to the PTO shaft 51 when the hydraulic effect isnot applied.

The pump case 30 is designed to be capable of accommodating the firstand second hydraulic pump bodies 20 a, 20 b, and the hydraulic clutchmechanism 55 of the PTO unit 50. More specifically, the pump case 30includes a hollowed case body 31 having first and second end walls 31 a,31 b respectively located closer to the first and second sides along thelongitudinal axis of the vehicle (front and rear sides in thisembodiment), and a peripheral wall 31 c extending between peripheraledges of the first and second end walls 31 a, 31 b.

The first end wall 31 a has on a first lateral side in the vehicle widthdirection a first opening 30 a, through which the first and secondhydraulic pump bodies 20 a, 20 b can pass into and out of the case body31, while the second end wall 31 b has on a second side in the vehiclewidth direction a second opening 30 b, through which the PTO unit 50 canpass into and out of the case body 31.

With the above arrangement, the case body 31 defines ahydraulic-pump-body-accommodation space 30A located closer to the firstlateral side of the vehicle in communication with the first opening 30a, and a hydraulic-clutch-mechanism-accommodation space 30B locatedcloser to the second lateral side of the vehicle in communication withthe second opening 30 b.

Preferably, the case body 31 has a partition wall 31 d for dividing thehydraulic-pump-body-accommodation space 30A from thehydraulic-clutch-mechanism-accommodation space 30B so as to effectivelyprevent metallic dust or the like generated by the frictional engagementbetween the friction plates in the hydraulic clutch mechanism 55 fromdirectly flowing into the hydraulic-pump-body-accommodation space 30A.

The pump case 30 further includes a lid member 32 connected to the casebody 31 so as to cover substantially the entire surface of the secondend wall 31 b located on the second side of the fore and aft directionof the vehicle, thereby closing the second opening 30 b. The lid member32 is connected to the second end wall 31 b, leaving an accommodationspace between the lid member 32 and the second end wall 31 b of the casebody 31. This accommodation space is to accommodate the transmissionmechanism 90 for operative connection between the input shaft 80 and thefirst pump shaft 10 a (the drive-side gear 91 and the driven-side gear92 in this embodiment) enabling them to be operated in association witheach other, and the transmission mechanism 60 for operative connectionbetween the first pump shaft 10 a and the second pump shaft 10 b (thefirst and second gears 61, 62 in this embodiment) enabling them to beoperated in association with each other. Preferably, filters or oilseals (not shown) are respectively provided in clearances between theinner circumferences of first- and second-pump-shaft-insertion holesprovided in the second end wall 31 b and the outer circumferences of thepump shafts 10 a, 10 b so that metallic dust or the like can beprevented from flowing into the hydraulic-pump-body-accommodation space30A.

The first opening 30 a is closed by the center section 40. That is, thecenter section 40 is connected to the first end wall 31 a so as to closethe first opening 30 a, while supporting the first and second hydraulicpump bodies 20 a, 20 b on a surface 40 a facing the case body 31.

Preferably, the first pump shaft 10 a has a downstream end with respectto the power transmission direction, which extends outwards through thecenter section 40, and a charge pump unit 70 is mounted on a surface 40b opposite to the hydraulic-pump-support surface 40 a so as to be driventhrough the downstream end of the first pump shaft 10 a. As usedthroughout the description, the directional term “upstream” and“downstream” are relative to the driving-power transmission direction.

In order to drive the charge pump unit 70, the second pump shaft 10 bmay be extended through the center section 40 to have an outside end,through which the charge pump unit 70 is driven. Alternatively, both thefirst pump shaft 10 a and the second pump shaft 10 b are extendedthrough the center section 40 to respectively have outside ends, so thatthe charge pump unit 70 is driven through either one of the outsideends, while a cooling fan (not shown) is driven through the residual oneof the outside ends. The charge pump unit 70 is used as a fluid-supplysource for supplying pressurized charge fluid to the hydraulic circuitbetween the first and second hydraulic pump bodies 20 a, 20 b and thehydraulic motor units 160 a, 160 b, as well as a fluid-supply source forsupplying operating fluid for the hydraulic clutch mechanism 55 in thePTO unit 50.

Preferably, the pump case 30 includes a seal plate 33 to be connected tothe first end wall 31 a. The seal plate 33 acts as a sealing means forliquid-tightly sealing a bearing hole for the PCT shaft 51 formed in thefirst end wall 31 a, and forms a part of the hydraulic circuit for fluidconnection between the charge pump unit 70 and the hydraulic clutchmechanism 55. The pump case 30 is thus liquid-tightly sealed by therespective parts so as to be capable of storing hydraulic fluid in theinner space.

Further, the PTO unit 50 preferably includes a hydraulic brake mechanism58 operable in association with clutching action of the hydraulic clutchmechanism 55 so as to be capable of effectively preventing the PTO shaft51 from continuing to rotate by inertia of the working unit 140connected thereto, when the hydraulic clutch mechanism 55 has disabledthe power transmission.

The hydraulic brake mechanism 58 includes a brake disc 58 a (an outercircumference of the driven-side member 55 c of the hydraulic clutchmechanism 55 in this embodiment) non-rotatable relative to the PTO shaft51, a brake shoe 58 b disposed so as to be capable of being frictionallyengaged with the brake disc 58 a, a brake pressing member 58 c having adistal end supporting the brake shoe 58 b and a proximal end axiallyslidably supported on a cylinder chamber 58A provided in the pump case30, and a brake biasing member 58 d for biasing the brake pressingmember 58 c so as to bring the brake shoe 58 b into frictionalengagement with the brake disc 58 a.

The thus arranged hydraulic brake mechanism 58 is of a negative brakesystem. That is, when the brake pressing member 58 c is not subjected tothe hydraulic effect, the brake shoe 58 b is held in frictionalengagement with the brake disc 58 a by the biasing force of the brakebiasing member 58 d, thereby applying braking force to the PTO shaft 51.On the other hand, when the brake pressing member 58 c is subjected tothe hydraulic effect, the brake pressing member 58 c is moved away fromthe brake shoe 58 b against the biasing force of the brake biasingmember 58 d, thereby applying no braking force to the PTO shaft 51.

More preferably, the cylinder chamber 58A is formed by the peripheralwall 31 c of the case body 31 and a cover 59 connected thereto. That is,the cylinder chamber 58A, which requires to provide liquid-tightcapability, is formed not in the case body 31 but in the cover 59.Whereby, it is not necessary to increase machining precision of the casebody 31, and hence it is possible to relatively easily form the casebody 31 by casting.

The application of the hydraulic effect to the brake pressing member 58c is made in association with the application of the hydraulic effect toclutch pressing member 55 e of the hydraulic clutch mechanism 55. Thatis, when the hydraulic clutch mechanism 55 is brought into “engagingstate” by hydraulic pressure applied to the clutch pressing member 55 e,the hydraulic brake mechanism is brought into “breaking-force releasingstate” since hydraulic pressure is also applied to the brake pressingmember 58 c. On the other hand, when hydraulic pressure is not appliedto the clutch pressing member 55 e and therefore the hydraulic clutchmechanism is brought into “disengaging state”, the hydraulic brakemechanism 58 is brought into “breaking-force applying state” sincehydraulic pressure is not applied also to the brake pressing member 58c.

Specifically, as illustrated in FIG. 2, the hydraulic brake mechanism 58and the hydraulic clutch mechanism 55 are controlled by a commonhydraulic source (the charge pump unit 70 in this embodiment) so as tobe operated in association with each other.

Now, the description will be made for the hydraulic circuit of the pumpunit 1 with reference to FIGS. 2 and 3.

The charge pump unit 70 has an inlet port 70 a connected to an optionaloutside tank 300 (see FIG. 2) or to the pump case 30, via a filter 310(see FIG. 2), and an outlet port 70 b connected to a mainpressurized-fluid line 320. The main pressurized-fluid line 320 isdivided into a charge line 321 and an operating fluid line 322 at apressure reducing valve 350 for charge pressure setting. Morespecifically, the main pressurized-fluid line 320 and the charge line321 are respectively connected to the upstream and downstream sides ofthe pressure reducing valve 350 so that surplus hydraulic fluidresulting from the pressure reducing operation of the pressure reducingvalve 350 flows into the operating fluid line 322.

Connected to the main pressurized-fluid line 320 are a pressure settingline 323 with a first relief valve 351 placed therein and a suction line324 with a check valve 352 placed therein. The suction line 324 isprovided to prevent occurrence of negative pressure in a hydrauliccircuit between the hydraulic pump bodies 20 and the hydraulic motorunits 160 (the pair of hydraulic lines 200 a and the pair of hydrauliclines 200 b in this embodiment) in the event of emergency or the like.

The charge line 321 is communicated respectively with the pair ofhydraulic lines 200 a and the pair of hydraulic lines 200 b via checkvalves 353. More specifically, the center section 40 has a pair ofhydraulic passages 201 a that respectively form parts of the pair ofhydraulic lines 200 a, and a pair of hydraulic passages 201 b thatrespectively form parts of the pair of hydraulic lines 200 b, in whichthe charge line 321 is communicated with the pair of hydraulic passages201 a and the hydraulic passages 201 b via the check valves 353 (seeFIG. 2).

Preferably, each of the pair of hydraulic passages 201 a and each thepair of hydraulic passages 201 b respectively have ends opening to theoutside through the same side of an peripheral wall of the centersection 40 to respectively form fluid connection ports for connectionwith the first and second hydraulic motor units 160 a, 160 b.

Further, the center section 40 has bypass lines 325 for communicationbetween the pair of hydraulic passages 201 a (i.e., between the pair ofhydraulic lines 200 a) and communication between hydraulic passages 201b (i.e., between the pair of hydraulic lines 200 b). Switching members354 for communication and shutoff between the pair of hydraulic passages201 a and between the pair of hydraulic passages 201 b are placed in thebypass lines 325 in such a manner as to be operable from the outside.The switching members 354 are used to force the pair of hydraulic lines200 a into communication with each other and the pair of hydraulic lines200 b into communication with each other, thereby allowing the motorshafts of the hydraulic motor units 160 a, 160 b to freely rotate, inthe event of failure of the pump unit or the like, where the vehiclemust be forcibly moved.

The operating fluid line 322 is communicated via a switching valve 360with a clutch line 326, which is in turn communicated with a brake line327. Accordingly, the switching valve 360 is controllable to supplypressurized hydraulic fluid and shut off the supply of the same from theoperating fluid line 322 to the clutch line 326 and the brake line 327,that is, to the hydraulic clutch mechanism 55 and the hydraulic brakemechanism 58 in association with each other.

Second relief valve 361 for pressure setting is placed in the clutchline 326 so as to set the maximum hydraulic pressure in each of theclutch line 326 and the brake line 327. The downstream side of thesecond relief valve 361 is communicated with the pump case 30.

The pressure reducing valve 350, the check valve 352, the first reliefvalve 351, the switching valve 360 and the second relief valve 361 aremounted in, for example, a charge pump case 72 of the charge pump unit70.

More preferably, the hydraulic brake mechanism 58 is provided with anaccumulator means 57 for absorbing switching shock caused when thehydraulic clutch mechanism 55 is switched from the power shutoff stateto the power transmission state (see FIG. 2). Specifically, the brakepressing member 58 c is provided with a rod 57 a having a proximal endlocated within the cylinder chamber 58A and a distal end on which thebrake shoe 58 b is supported, a pressure receiving plate 57 b axiallysidably supported on the rod 57 a and arranged so as to divide thecylinder chamber 58A into a pressurized-fluid actuation chamber and abiasing-member accommodation chamber, and a follow plate 57 c axiallynon-movably supported on the rod 57 a so as to be located within thebiasing-member accommodation chamber.

The pressure receiving plate 57 b has an orifice 57 b′ for communicationbetween the pressurized-fluid actuation chamber and the biasing-memberaccommodation chamber. The orifice 57 b′ is closed by the follow plate57 c when it has been pressed by a predetermined stroke upon receivingthe effect of pressurized hydraulic fluid.

The thus provided accumulator means 57 can produce the followingeffects:

When the switching valve 360 is held at the pressurized-fluid supplyposition so as to bring the hydraulic clutch mechanism 55 into the“engaging state”, while bringing the hydraulic brake mechanism 58 intothe “breaking-force releasing state”, pressurized hydraulic fluid issupplied into the clutch line 326 and the brake line 327. In an initialstage in which pressurized hydraulic fluid has started to be suppliedinto the pressurized-fluid actuation chamber via the brake line 327,pressurized hydraulic fluid leaks through the orifice 57 b′. Thisleakage allows the hydraulic pressure of the clutch line 326 and thebrake line 327 to relatively gradually increase. Accordingly, relativelygentle clutch engagement of the hydraulic clutch mechanism 55 isachieved. Then, the pressure receiving plate 57 b is pressed throughpressurized hydraulic fluid, thereby closing the orifice 57 b′.Accordingly, the hydraulic pressure of the clutch line 326 and the brakeline 327 is increased to a set value of the second relief valve 361.

Thus, in this embodiment, hydraulic pressure in the clutch line 326 canbe gradually increased until the orifice 57 b′ is closed by the pressurereceiving plate 57 b after it is pressed by a predetermined stroke.Accordingly, it is possible to prevent abrupt clutch engagement of thehydraulic clutch mechanism 55, and hence wear-out and damages of therespective parts.

In addition to the effects as described above, the thus arranged pumpunit 1 can produce the following effects:

By the pump unit 1, which is so arranged that pressurized hydraulicfluid can be supplied into the hydraulic motor units 160 a, 160 b bydriving power from the driving source 150, and driving power from thedriving source 150 is taken out by the PTO shaft 51 and outputtherefrom, the main transmission path and the sub transmission path thatcan be controlled independently of each other can be easily formed.

The above described arrangement, which makes the hydraulic clutchmechanism 55 accommodated within the pump case 30 enable and disable thepower transmission in the sub transmission path, contributes to animproved durability as compared with a conventional arrangement, whichmakes an electromagnetic clutch perform the same function.

Further, the above described arrangement, in which the supply ofpressurized hydraulic fluid to the hydraulic clutch mechanism 55 is madeby the charge pump unit 70 connected to the pump case 30 and driven bythe first pump shaft 10 a, can contribute to a shortened andpressurized-fluid supply circuit.

It is a matter of course that the respective constitutional elements ofthe pump unit 1 are not necessarily limited to those in this embodiment,but can be subjected to various modifications or replacement withothers. For example, in place of the hydraulic brake mechanism 58, ahydraulic brake mechanism 58′ as illustrated in FIG. 5 can be used. Thehydraulic brake mechanism 58′ includes a friction brake plate 58 a′relatively non-rotatably and axially slidably supported on the PTO shaft51, a fixed friction plate 58 b′ fixed to the case body 31, and a brakepressing member 58 c′ for pressing both the friction plates 58 a′, 58into contact with each other, in which the brake pressing member 58 c′is designed to be operated in association with the clutch pressingmember 55 e via a connection member 58 d′.

That is, when the clutch pressing member 55 e is pressed by thehydraulic effect so as to bring the drive-side friction plate 55 b intofrictional engagement with the driven-side friction plate 55 d, thebrake pressing member 58 c′ is moved away from the friction brake plate58 a′ and the fixed friction plate 58 b′ in association with the actionof the clutch pressing member 55 e. On the other hand, when the clutchpressing member 55 e is moved away from the drive-side friction plate 55b and the driven-side friction plate 55 d by the effect of the clutchbiasing member 55 f, the brake pressing member 55 c′ brings the frictionbrake plate 58 a′ into frictional engagement with the fixed frictionplate 58 b′ in association with the action of the clutch pressing member55 e. With the arrangement using the thus constructed hydraulic brakemechanism 58′, it is also possible to effectively prevent the PTO shaft51 from continuing to rotate by inertia even after power to the PTOshaft 51 has been shut off.

Second Embodiment

The description will be made for the second embodiment of the presentinvention with reference to the accompanied drawings. FIG. 6 is a planview of a lawn mower 100B, to which a pump unit 2 of this embodiment hasbeen applied, and FIG. 7 is a plan view in horizontal cross section ofthe pump unit 2 according to this embodiment. In the followingdescription, corresponding or identical parts to those of the firstembodiment have been given the same reference characters to omit adetailed description thereof.

While the pump unit 1 of the first embodiment is fixedly supported bythe vehicle frame 110, the pump unit 2 of this embodiment is integrallyconnected to the driving source 150, as illustrated in FIGS. 6 and 7.

As illustrated in FIG. 7, the driving source 150 has a mount flange 151,to which a flywheel housing 157 is connected. The flywheel housing 157has a peripheral wall 157 a connected to the mount flange 151 andextending in the power transmission direction (in the fore and aftdirection of the vehicle in this embodiment), and end wall 157 bextending from a downstream end (a front end in this embodiment) of theperipheral wall 157 a.

The case body 31 is connected to the flywheel housing 157 via the secondend wall 31 b in a free state relative to the vehicle frame 110.Preferably, the second end wall 31 b of the case body 31 is connected tothe end wall 157 b of the flywheel housing 157, leaving a spacetherebetween. The space acts as an accommodation space for the first andsecond gears 61, 62, the drive-side gear 91 and the driven-side gear 92.In this embodiment, the end wall 157 b of the flywheel housing 157 has arecess, which forms the accommodation space.

The input shaft 80 has an upstream end directly connected to an outputpart of the damper 156 in the flywheel 155, while beingbearing-supported by the end wall 157 b of the flywheel housing 157.Reference numeral 152 in FIG. 7 represents an output shaft of thedriving source 150.

In addition to the effects in the first embodiment, the pump unit 2produces the following effects:

The pump unit 2, which is integrally connected to the driving source 150that is supported on the vehicle frame 110 in vibration free manner,does not cause vibration difference between the driving source 150 andthe pump unit 2. As a result, it is possible to omit thevibration-absorbing transmission means between the driving source 150and the pump unit 1, which is used in the first embodiment, therebyachieving reduced production cost. Also, the length between the drivingsource 150 and the pump unit 2 can be shortened. Since vibrations due topulsation of hydraulic fluid cased by the actuation of the hydraulicpump bodies 20 a, 20 b are absorbed by utilizing a vibration absorptionmaterial interposed between the driving source 150 and the vehicle frame110, vibrations are unlikely to transmit to the vehicle body, whichcontributes to improved driving environment.

Third Embodiment

The description will be made for the third embodiment of the presentinvention with reference to the accompanied drawings. FIGS. 8A and 8Bare a side view and a plan view of a lawn mower 100C, to which a pumpunit 3 of the third embodiment has been applied. FIGS. 9 and 10 are aplan view in horizontal cross section and a side view in vertical crosssection of the pump unit 3 of the third embodiment. FIG. 11 is a crosssection taken along the line XI—XI in FIG. 9. In the followingdescription, corresponding or identical parts to those of the first orsecond embodiment have been given the same reference characters to omita detailed description thereof.

In the pump unit 3 of this embodiment, the PTO shaft in the pump unit 1of the first embodiment is modified so as to extend in the verticaldirection. More specifically, the pump unit 3 of this embodimentincludes a PTO unit 450 in place of the PTO unit 50, and a pump case 430in place of the pump case 30.

The PTO unit 450 includes a PTO shaft 451 that extends vertically so asto be substantially orthogonal to the input shaft 80 arranged parallelto the longitudinal axis of the vehicle and that has the same axialposition in the width direction of the vehicle as the input shaft 80,and a hydraulic clutch mechanism 455 for enabling and disabling powertransmission from the input shaft 80 to the PTO shaft 451.

The PTO shaft 451 has a downstream end supported by the pump case 430 soas to extend vertically and outwardly through the pump case 430. In thisembodiment, as best illustrated in FIGS. 10 and 11, the downstream endextends downwards from the pump case 430. The downstream end of the PTOshaft 451 is operatively connected to the input part of the working unit140 via the vibration-absorbing transmission means in the same manner asthe first embodiment. In this embodiment, as the vibration-absorbingtransmission means, a belt transmission mechanism 176 is employed (seeFIGS. 10 and 11).

The hydraulic clutch mechanism 455 includes a drive-side member 455 athat is relatively rotatably and axially non-slidably supported on thePTO shaft 451, and operatively connected to the first pump shaft 10 a.In this embodiment, as described above, the PTO shaft 451 is locatedorthogonal to the input shaft 80 so that the drive-side member 455 a isoperatively connected to the input shaft 80 via a direction-changingpower transmission mechanism 460. In this embodiment, thedirection-changing power transmission mechanism 460 includes a bevelgear provided to the drive-side member 455 a, and an intermediate bevelgear 463 relatively non-rotatably supported on the input shaft 80 inmeshed engagement with the bevel gear. In this embodiment, thedrive-side gear 91, which is relatively non-rotatably supported on theinput shaft 80, is arranged to be meshed with the first gear 61, whichis relatively non-rotatably supported on the first pump shaft 10 a, sothat the input shaft 80 and the first pump shaft 10 a are operativelyconnected to each other via the drive-side gear 91 and the first gear61.

The pump case 430 is a modified form resulting from a partialmodification of the pump case 30 in order to accommodate the PTO unit450. That is, as best illustrated in FIGS. 9 and 10, a case body 431 inthe pump case 430 has an intermediate wall 431 d, which extends from theperipheral wall 31 c towards an opposite side to thehydraulic-pump-body-accommodation space 30A. The intermediate wall 431 dand the lid member 32 together act as a bearing of the input shaft 80.In this embodiment, the second opening 30 b, through which the hydraulicclutch mechanism 455 can pass, is located above the intermediate wall431 d (see FIG. 10).

The pump case 430 in this embodiment includes a seal cap 433 connectedto a bottom of the case body 431, in place of the seal plate 33. In thisembodiment, a pressurized-fluid supply line to the hydraulic clutchmechanism 455 and the hydraulic brake mechanism 58 (the clutch line 326and the brake line 327) is formed in the case body 431 (see FIG. 11).The operating fluid line 322, which extends through the switching valve360 located in the charge pump unit 70, is connected to thepressurized-fluid supply line via conduit (not shown).

The same effects as those in the first embodiment can also be producedin this embodiment. Although the pump case 430 is fixedly supported onthe vehicle frame 110 with a distance away from the driving source 150in this embodiment. Alternatively, the pump case 430 can be integrallyconnected to the driving source 150 in the same manner as in the secondembodiment (see FIGS. 12 and 13). While the above embodiments weredescribed by taking for example the case where the pump unit is operatedin association with the driving source 150 of a horizontal type, whichhas a horizontally extending output shaft, the pump unit in eachembodiment can be designed to be capable of being operated inassociation with a driving source of a vertical type, which has avertically extending output shaft.

Forth Embodiment

The description will be made for the fourth embodiment of the presentinvention with reference to the accompanied drawings. FIGS. 14A and 14Bare a side view and a plan view of a lawn mower 100D, to which a pumpunit 4 of this embodiment has been applied. FIG. 15 is a hydrauliccircuit diagram of the pump unit 4. FIGS. 16 and 17 are a plan view inhorizontal cross section and a side view in vertical cross section ofthe pump unit 4 according to this embodiment. FIGS. 18 and 19 are crosssections respectively taken along the line XVIII—XVIII and XIX—XIX inFIG. 16. In the following description, corresponding or identical partsto those of the aforementioned embodiments have been given the samereference characters to omit a detailed description thereof.

The pump unit 4 of this embodiment is designed to omit the necessity toprovide the input shaft 80 in the pump unit 1 of the first embodiment,and input driving power from the driving source 150 to the first pumpshaft 10 a.

That is, as illustrated in FIGS. 16 and 17, the pump unit 4 includes thefirst pump shaft 10 a operatively connected to the driving source 150,the first hydraulic pump body 20 a driven by the first pump shaft 10 a,the second pump shaft 10 b operatively connected to the first pump shaft10 a, the second hydraulic pump body 20 b driven by the second pumpshaft 10 b, the pump case 30 having the first opening 30 a, throughwhich the first hydraulic pump body 20 a and the second hydraulic pumpbody 20 b can pass into and out of the pump case 30, the center section40 connected to the pump case 30 so as to close the first opening 30 a,while supporting the first and second hydraulic pump bodies 20 a, 20 b,and the PTO unit 50 accommodated in the center section 40.

As best illustrated in FIG. 16, the first pump shaft 10 a is supportedby the pump case 30 so as to have the upstream end (rear end in thisembodiment) extending outwards through the pump case 30, and isoperatively connected to the driving source 150 via the flywheel 155.

In this embodiment, in the same manner as the first embodiment, asillustrated in FIG. 14, the driving source 150 is supported on thevehicle frame 110 in vibration free manner, while the pump case 30 isfixedly supported on the vehicle frame 110. Accordingly, the drivingsource 150 and the first pump shaft 10 a are operatively connected toeach other via the vibration-absorbing transmission means.

The second pump shaft 10 b is supported by the pump case 30 so as to bearranged substantially parallel to the first pump shaft 10 a. In thisembodiment, the second pump shaft 10 b is operatively connected to thefirst pump shaft 10 a via the transmission mechanism 60 placed in thepump case 30 so as to be rotated synchronously with the first pump shaft10 a. In this embodiment, the transmission mechanism 60 includes thefirst gear 61 relatively non-rotatably supported on the first pump shaft10 a, and the second gear 62 having the same pitch as the first gear 61and relatively non-rotatably supported on the second pump shaft 10 b soas to be in meshed engagement with the first gear 61.

The hydraulic clutch mechanism of the pump unit 4 of this embodiment isthe same as that of the first embodiment, except that the powertransmission from the first pump shaft 10 a to the PTO shaft 51 isselectively enabled and disabled. That is, the hydraulic clutchmechanism 55 of this embodiment is the same as that of the firstembodiment except that the drive-side member 55 a is operativelyconnected not to the input shaft 80 but to the first pump shaft 10 a.

The thus arranged hydraulic clutch mechanism 55 enables powertransmission from the first pump shaft 10 a to the PTO shaft 51 via thedrive-side member 55 a and the driven-side member 55 c when the clutchpressing member 55 e has brought the drive-side friction plate 55 b andthe driven-side friction plate 55 d into frictional engagement with eachother by the hydraulic effect, and disables power transmission from thefirst pump shaft 10 a to the PTO shaft 51 when it is not subjected tothe hydraulic effect.

The pump unit 4 of this embodiment has the pump case 30, which is thesame as the pump case of the first embodiment except that thetransmission mechanism 90 is not placed therein. That is, in thisembodiment, an accommodation space between the lid member 32 and thesecond end wall 31 b of the case body 31 is designed to accommodate onlythe transmission mechanism 60 for operative connection between the firstpump shaft 10 a and the second pump shaft 10 b enabling them to beoperated in association with each other.

The pump unit 4 of this embodiment produces the same effects as those ofthe first embodiment. Also, in this embodiment, various modificationsand replacements can be made in the same manner as those in the firstembodiment. For example, as illustrated in FIG. 20, it is possible toprovide the hydraulic brake mechanism 58′ in place of the hydraulicbrake mechanism 58 described in the first embodiment.

In this embodiment, as best illustrated in FIG. 14B, the first pumpshaft 10 a of the pump unit 4 and the output shaft of the driving source150 are located along the longitudinal center axis of the vehicle. As aresult, the PTO shaft 51 offset from the first pump shaft 10 a to eitherside relative to the longitudinal center axis of the vehicle, and theinput shaft of the working unit 140 located substantially along thelongitudinal axis of the vehicle are offset from each other in the widthdirection of the vehicle. Alternatively to this arrangement, it is amatter of course to locate the PTO shaft 51 along the longitudinalcenter axis of the vehicle, as illustrated in FIG. 14C. Where the PTOshaft 51 is located substantially along the longitudinal center axis ofthe vehicle, the first pump shaft 10 a is necessarily offset from theoutput shaft of the driving source 150 in the width direction of thevehicle. Therefore, in this arrangement, preferably, the first pumpshaft 10 a is operatively connected to the output shaft of the drivingsource 150 via a belt transmission mechanism.

Fifth Embodiment

The description will be made for the fifth embodiment of the presentinvention with reference to the accompanied drawings. FIGS. 21A and 21Bare a side view and a plan view of a lawn mover 100E, to which a pumpunit 5 of this embodiment has been applied. FIG. 21C is a plan view ofthe lawn mower, to which the pump unit according to a modified exampleof this embodiment has been applied. FIG. 22 is a plan view inhorizontal cross section of the pump unit 5 according to thisembodiment. FIGS. 23 and 24 are cross sections respectively taken alongthe line XXIII—XXIII and the line XXIV—XXIV in FIG. 22. In the followingdescription, corresponding or identical parts to those of theaforementioned embodiment have been given the same reference charactersto omit a detailed description thereof.

The pump unit 5 of this embodiment is modified so as to have the PTOshaft extending in the vertical direction in the pump unit 4 of thefourth embodiment. More specifically, the pump unit 5 of this embodimenthas the PTO unit 450 and the pump case 430 of the fourth embodiment inthe pump unit 4 of the fourth embodiment.

The thus arranged pump unit 5 can produce the same effects as those inthe pump unit 4 of the fourth embodiment.

It is a matter of course that the pump unit 5 can be supported on thevehicle frame 110 so as to have the PTO shaft 451 placed substantiallyin the middle of the width of the vehicle, instead of having the pumpunit 5 supported on the vehicle frame 110 so as to have the first pumpshaft 10 a placed in the same position as the longitudinal center axisof the vehicle in the vehicle width direction (see FIG. 21C).

Sixth Embodiment

The description will be made for the sixth embodiment of the presentinvention with reference to the accompanied drawings. FIGS. 25A and 25Bare a side view and a plan view of a lawn mower 100F, to which a pumpunit 6 of this embodiment has been applied. FIG. 26 is a side view invertical cross section of the pump unit 6 according to this embodiment.In the following description, corresponding or identical parts to thoseof the aforementioned embodiments have been given the same referencecharacters to omit a detailed description thereof.

While the pump units 4, 5 of the fourth and fifth embodiments each aredesigned to be operated in association with the driving source 150,which is a horizontal type that has the horizontally extending outputshaft, the pump unit 6 of the sixth embodiment is designed to beoperated in association with the driving source 150′, which is avertical type that has the vertically extending output shaft.

Specifically, as illustrated in FIG. 26, the first pump shaft 10 a isextended in the vertical direction. In this embodiment, the first pumpshaft 10 a has a lower end extending downwards from a pump case 530 andoperatively connected to the driving source 150′ via a belt transmissionmechanism 171.

The pump case 530 is the same in construction as the pump case 30 in thefourth embodiment, except that the pump case 530 is oriented in adifferent direction. That is, the pump case 530 is fixed to the vehicleframe 110 so as to have the first and second end walls 31 a, 31 bupwardly and downwardly oriented in the vertical direction.

The PTO shaft 51 is supported by the pump case 530 so as to extendsubstantially parallel to the first pump shaft 10 a, and has a lowerextension, which extends downwards from the pump case 430. In thisembodiment, the lower extension of the PTO shaft 51 is operativelyconnected to the working unit 140 via the belt transmission mechanism176.

In the thus arranged sixth embodiment, the same effects as those of thefourth and fifth embodiments can be produced. While the PTO shaft 51 isarranged so as to extend in the vertical direction in this embodiment,it is a matter of course that the PTO shaft 51 can be arranged so as toextend in the fore and aft direction of the vehicle. In thisarrangement, the direction-changing power transmission mechanism 460 asdescribed in the third embodiment is provided. In this embodiment, theoutput shaft of the driving source 150′ and the first pump shaft 10 aare arranged substantially along the longitudinal center axis of thevehicle (see FIG. 25B). Alternative to this, the PTO shaft 51 may bearranged substantially in the middle of the width of the vehicle.

Seventh Embodiment

The description will be made for the seventh embodiment of the presentinvention with reference to the accompanied drawings. FIG. 27 is a planview of a lawn mower 100G, to which a pump unit 7 of this embodiment hasbeen applied. FIG. 28 is a plan view in horizontal cross section of thepump unit 7 according to this embodiment. In the following description,corresponding or identical parts to those of the aforementionedembodiments have been given the same reference characters to omit adetailed description thereof

The pump unit 7 of this embodiment has been conceived based upon theconcept of integral connection between the pump unit and the drivingsource as described in the second embodiment, which is applied to thepump unit arrangement in each of the fourth to sixth embodiments.

With the thus arranged pump unit 7, the same effects as those in thesecond embodiment, as well as the same effects as those in the fourthand fifth embodiments can be produced. While this embodiment has beendescribed by taking for example the case where the PTO shaft 51 isarranged so as to be substantially parallel to the first pump shaft 10a, a PTO shaft 451, which extends substantially orthogonal to the firstpump shaft 10 a, may be provided.

Further, this embodiment has been described by taking for example thecase where the pump unit is integrally connected to the driving source150 of the horizontal type. However, it is a matter of course that thepump unit is integrally connected to the driving source 150′ of thevertical type.

This specification is by no means intended to restrict the presentinvention to the preferred embodiments set forth therein. Variousmodifications to the pump unit, as well as the working vehicle asdescribed herein, may be made by those skilled in the art withoutdeparting from the spirit and scope of the present invention as definedin the appended claims.

1. A working vehicle comprising: a vehicle frame; a first pair oflaterally disposed wheels supported by said vehicle frame; a second pairof laterally disposed wheels supported by said vehicle frame so as to belocated away from said first pair of laterally disposed wheels in a foreand aft direction of said working vehicle; a working unit supported bysaid vehicle frame; a driving source supported by said vehicle frame;first and second motor units respectively and operatively connected tosaid first pair of laterally disposed wheels; and a pump unit supporteddirectly or indirectly byialld vehicle frame so as to be operativelyconnected to said driving source, said pump unit arranged to supply anddischarge hydraulic fluid into and from each of said first and secondmotor units, and take out driving power of said driving source andoutput the same as driving power for said working unit, said pump unitcomprising: an input member operatively connected to said drivingsource; a first hydraulic pump body operatively connected to said inputmember; a pump case for accommodating said first hydraulic pump body;fluid connection ports disposed on an outside surface of said pump casefor fluidly connecting said first hydraulic pump body with said firstand second motor units; and a PTO unit accommodated within said pumpcase, said PTO unit comprising: a PTO shaft supported by said pump caseso as to have an end extending outward from said pump case; and a clutchmechanism for selectively enabling and disabling transmission of drivingpower from said input member to said PTO shaft, wherein said first andsecond motor units are accommodated outside said pump case so as to belocated away from said pump unit.
 2. A working vehicle according toclaim 1, further comprising a charge pump unit that is operativelyconnected to said input member.
 3. A working vehicle according to claim1, wherein said pump unit further comprises a second hydraulic pump bodyoperatively connected to said input member, and said fluid connectionports include first fluid connection ports that are for said firsthydraulic pump body to fluidly connect with said first motor unit andsecond fluid connection ports that are for said second hydraulic pumpbody to fluidly connect with said second motor units, said first andsecond fluid connection ports being arranged on the outside surface ofsaid pump case.
 4. A working vehicle according to claim 1, wherein saidPTO unit further comprises a brake mechanism for releasing and applyingbraking force away from and to said PTO shaft in association with theoperation of the clutch mechanism to enable and disable the transmissionof driving power from said input member to said PTO shaft.
 5. A workingvehicle according to claim 1, wherein said driving source is supportedon said vehicle frame so as to be capable of vibrating with respect tosaid vehicle frame; and said driving source is operatively connected tosaid input member via vibration-absorbing transmission means.
 6. Aworking vehicle according to claim 1, wherein said driving source issupported on said vehicle frame so as to be capable of vibrating withrespect to said vehicle frame; and said pump unit is integrallyconnected to said driving source in a free state relative to the vehicleframe.
 7. A working vehicle according to claim 1, wherein said pump unitfurther comprises an input shaft acting as said input member; and afirst pump shaft operatively connected to said input shaft and arrangedto drive said first hydraulic pump body.
 8. A working vehicle accordingto claim 7, wherein said PTO shaft is arranged coaxially with said inputshaft.
 9. A working vehicle according to claim 7, wherein said PTO shafthas an axis, which is located at the same position as an axis of saidinput shaft in a vehicle width direction, and is arranged substantiallyorthogonal to said axis of said input shaft.
 10. A working vehicleaccording to claim 1, wherein said pump unit further comprises a firstpump shaft that acts as said input member and is arranged to drive saidfirst hydraulic pump body.
 11. A working vehicle according to claim 10,wherein said first pump shaft is arranged substantially parallel to saidPTO shaft.
 12. A working vehicle according to claim 10, wherein saidfirst pump shaft is arranged substantially orthogonal to said PTO shaft.13. A working vehicle according to claim 1, wherein said pump case has afirst end wall with a first opening through which said first hydraulicpump body can pass, a second end wall with a second opening throughwhich said clutch mechanism can pass, said second end wall beingdisposed away from said first end wall along an axial direction of saidinput member, and a partition wall extending said first end wall andsaid second end wall, said pump unit further comprising a center sectionconnected to said first end wall so as to close said first opening anddefine a hydraulic-pump-body-accommodation space for accommodating saidfirst hydraulic pump body in cooperation with said second end wall andsaid partition wall, said center section supporting said first hydraulicpump body on one of opposite sides thereof and forming said hydrauliccircuit, and a lid member connected to said second end wall so as toclose said second opening and define ahydraulic-clutch-mechanism-accommodation space for accommodating saidclutch mechanism in cooperation with said first end wall and saidpartition wall.